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Geez, Norm, you must be psychic. I wish you'd posted that yesterday. I looked all over for that same thing this morning before finding it.

I was trying to figure out why they didn't make direct reading analog pressure type micron gauges. After finding out that there are over 3/4 of a million microns between zero and 30" inches of vacuum, I realized that in order to display the graduations at 1/10" apart, it would take over 1 mile of gauge space to accomodate them. Guess I need a bigger truck!!

Actually most of the digital ones only go from 50-5000, but still.....

Originally posted by midhvac Geez, Norm, you must be psychic. I wish you'd posted that yesterday. I looked all over for that same thing this morning before finding it.

I was trying to figure out why they didn't make direct reading analog pressure type micron gauges. After finding out that there are over 3/4 of a million microns between zero and 30" inches of vacuum, I realized that in order to display the graduations at 1/10" apart, it would take over 1 mile of gauge space to accomodate them. Guess I need a bigger truck!!

Actually most of the digital ones only go from 50-5000, but still.....

Zero microns is a perfect vacuum. Since there are 25,400 microns per inch, a micron gauge at atmospheric pressure would read 762,000 microns. So the micron gauges don't start indicating microns until we get down to 5000 microns or so. By limiting the instrument range the accuracy is increased and the cost of the instrument is decreased.